1. Field of the Invention
The present invention relates to semiconductor devices and circuits and, more particularly, to compliant contact pins and methods of fabrication for connecting electrical signals to integrated circuits.
2. State of the Art
Semiconductor devices, from microprocessors to memory chips, are fabricated by performing a long series of processes and steps including etching, masking, depositing, and the like, on a semiconductor wafer or other bulk semiconductor substrate. Many integrated circuits may be fabricated on a single semiconductor wafer by placing them in arrays across the wafer. Ultimately, the individual circuits are singulated from the wafer and are either further processed, including packaging and additional testing, or discarded when they are determined to be undesirable.
Due to processing or other defects in the semiconductor wafer, certain ones of the integrated circuits may not function as designed. Such defects may be detected initially or may not become apparent until the integrated circuit has been in operation for a period of time. Therefore, it is important to test and electrically stress the integrated circuits to determine which circuits are operational and which ones are defective or are likely to become defective.
Semiconductor integrated circuits are typically subjected to a series of test procedures during the manufacturing process in order to verify functionality and reliability. Typical test approaches include wafer probe testing in which integrated circuits are individually tested to determine the operational characteristic of each before singulation from the semiconductor wafer.
Conventionally following initial testing, the integrated circuits are singulated into individual integrated circuit chips with the operational chips being further assembled into packages. The packaged devices are then “burned-in” by loading the packaged devices into sockets on burn-in boards and electrically operating the packaged devices at elevated temperatures for an extended testing period. Such elevated temperatures induce failure in marginally operative or nonoperative devices, which allows such devices to be screened-out and discarded before they are integrated into higher level assemblies or sold. Burning-in and testing of packaged devices are typically accomplished through the use of sockets suited for the burn-in conditions and high speed testing. Accordingly, conventional manufacturing and testing processes are expensive and time consuming because of the repeated handling and testing of individual devices: therefore, individually tested and handled devices that ultimately fail have wasted costly resources and time.
A considerable advantage in cost and in process time could be attained by burning-in and testing a semiconductor wafer before it is singulated into discrete devices. Additional savings may be recognized by forgoing packaging of devices that ultimately fail once subjected to burn-in conditions. A considerable effort has been expended to develop effective methods for wafer level testing. One such approach utilizes cantilevered or spring-wire probes that are arranged on a contact or probe card for simultaneous contact to all of the devices on the semiconductor wafer. Such contactor cards are expensive to manufacture and result in undesirable electrical characteristics such as increased inductance along parallel wires.
Therefore, there is a need for providing a contact methodology that results in a highly economically manufacturable method of contacting individual semiconductor devices in a wafer level testing environment.
Furthermore, individual dice generally need to be packaged into a higher assembly before they may be integrated into a system environment. These higher assemblies or packages generally need to accommodate or compensate for differences in thermal expansion between the individual die and the system level substrate. Therefore, there is a need for providing a contact methodology that mediates stresses between dissimilar materials.